SGV Serotype Isolates of Barley Yellow Dwarf Virus Differing in Vectors and Molecular Relationships

Abstract

Two SGV serotype isolates of barley yellow dwarf virus (BYDV), NY-SGV from New York State and TX-SGV from Texas, exhibited differences in aphid transmissibility that could significantly influence their relative occurrence and epidemiology; i.e., TX-SGV was readily transmitted by a range of vector aphids, whereas NY-SGV showed a much greater vector specificity. In serological assays, TX-SGV differed from NY-SGV but resembled an SGV serotype isolate from Idaho that shares similar vector relationships with TX-SGV. Dot blot hybridization assays using cloned cDNA probes distinguished the SGV isolates from the P-PAV, MAV-PS1, NY-RPV, and NY-RMV isolates of BYDV and from each other. Nucleotide sequences were determined for the 22-kDa coat protein gene, the associated 17-kDa internal open reading frame, and a 50-kDa protein gene of the NY-SGV and TX-SGV isolates. The deduced amino acid sequences of these proteins shared approximately 96% similarity between isolates but had only about 71% similarity with comparable regions from the MAV-PSI and P-PAV serotype isolates and approximately 57% similarity with those of the NY-RPV isolate. These comparisons did not identify obvious differences in primary structure that might be related to differences in vector relationships of NY-SGV and TX-SGV. The results demonstrate that the SGV serotype is distinct from other BYDV serotypes and that it includes sequence-distinguishable variants that differ in epidemiologically significant properties, such as transmissibility by various vectors.